Most commercial, hair setting compositions include film forming polymers (fixatives), viscosity increasing polymers, and polymer modifiers, in addition to solvents, co-solvents, and cosmetic adjuvants, such as preservatives, color, fragrance, and the like. The amount of fixative polymer present in a particular hair setting composition can vary in the range of about 0.2 to about 10 weight percent, depending on the attributes desired during application and the function of the product. See, for example, Ch. 30, Harry's Cosmeticology, 8th Ed., M. J. Rieger, Ph.D. (ed.), 666-667, Chemical Publishing Co., Inc., New York, N.Y. (2000).
A common type of hair setting composition contains an aqueous based gel containing the fixative polymer which when applied to the hair “fixes” the hair in a desired configuration upon drying. The fixative polymer is deposited on the individual hair filaments as a thin film which encases the hair filaments tending to keep the hair in the configuration in which it has been set. In addition, in places where hair filaments overlap and touch the fixative acts as an adhesive to bind the hair filaments together, helping to hold the desired set.
In order to be effective, the fixative polymer must meet a number of rigid requirements. The films derived from these polymers should be flexible and yet possess strength and elasticity. They should display good adhesion to the hair so as to avoid dusting or flaking off over extended periods of time or when the hair is subjected to stresses such as brushing or combing. Moreover, polymeric fixative films should not interfere with the brushing or combing of the hair, and should remain free of tack or stickiness under humid conditions. Applied fixative films should also be transparent, glossy, maintain clarity upon aging, and be easily removable when washing with a hair cleanser and water.
Also of importance are the aesthetic characteristics and appearance of hair setting compositions before, during, and after application to hair. In addition, the product viscosity should be non-runny to avoid dripping from opened and inverted product containers such as tubes and jars and from the fingers prior to application to the hair. Product clarity is preferably substantially transparent or clear in order to obtain a “clean” product appearance. The product should be shear thinning for easy application, have a smooth texture, a non-tacky feel, and be able to dry relatively quickly on the hair.
Conventional polymeric hair styling or hair fixative polymers, well known in the art, include natural gums and resins and neutral and anionic polymers of synthetic origin. Some commercially available neutral and anionic polymers, which have been used as hair styling or fixative polymers include, for example, polyvinylpyrrolidone (PVP), polyvinylpyrrolidone/vinylacetate copolymer (PVP/VA), and acrylates/hydroxyesters acrylates copolymers (Rohm and Haas). Acrylates Copolymer (Balance CR, Akzo; Luviflex Soft, Luvimer 100P, and Luvimer Pro 55 marketed by BASF), AMP-Acrylates/Allyl Methacrylate Copolymer (Fixate™ G-100, Lubrizol Advanced Materials, Inc.), Polyacrylate-14 (Fixate™ Plus, Lubrizol Advanced Materials, Inc.), and Polyacrylate-2 crosspolymer (Fixate™ Superhold, Lubrizol Advanced Materials, Inc.) are other examples of anionic styling polymers. For example, U.S. Pat. No. 4,196,190 to Gehman, et al., discloses an acrylic hair fixative resin made via emulsion polymerization techniques containing between 10 to 30 weight % of an alkyl acrylate, between 41 to 60 weight % of methyl methacrylate, between 5 to 20 weight % of hydroxyethyl methacrylate, and between 10 to 30 weight % of methacrylic acid. Acrylates/acrylamide copolymers (Ultimer® CG 700 from Nalco Company), Acrylic Acid/VP Crosspolymer (Ultrathix™ P-100, ISP), ethyl and butyl esters of polyvinyl methyl ether/maleic anhydride copolymer (PVM/MA) (GANTREZ®, ISP), and a copolymer of vinylpyrrolidone/acrylic acid/lauryl methacrylate (STYLEZE™ 2000, ISP) are other examples.
One of the shortcomings of conventional fixative polymers is that they generally do not provide significant thickening or contribute significant rheological properties at practical use concentrations. Consequently, conventional hair setting compositions typically require, in addition to the hair setting or fixative polymer, the addition of one or more viscosity increasing thickeners or gellants to provide a more convenient or pleasing product or to cause the preparation to be retained on the hair while the carrier vehicle evaporates. Typical thickeners or gellants that have been employed in the art include natural gums, synthetic polymers and other rheology modifying additives, such as emulsifiers, waxes, and the like, to achieve the desired rheological gel properties. A few examples of synthetic and natural polymers that have been used as gellants in commercial hair fixative products include Carbomers (crosslinked polyacrylic acid polymers) and hydrophobically modified derivatives thereof, sold under the registered trademark Carbopol®, such as Carbopol® 980 polymer, Carbopol® 940 polymer, Carbopol® Ultrez 10 polymer, Carbopol® Ultrez 21 polymer, Carbopol® Ultrez 20 polymer, Carbopol® ETD 2020 polymer, and the like marketed by Lubrizol Advanced Materials, Inc., hydrophobically modified cellulose, xanthan gum and hydrophobically modified, alkali-swellable, emulsion polymers (HASE polymers).
However, conventional anionic hair setting and hair fixative polymers frequently are incompatible with the rheology modification agent or gellant, resulting in loss of viscosity, lack of gel product clarity, unpleasant texture properties (e.g., gelatin like, crumbly, gooey, slimy, runny and/or stringy texture profiles) and loss of shear thinning rheology. Polymers possessing shear thinning rheology will, upon exposure to shear stress, show a decrease in viscosity, allowing easier delivery and application to and on the target substrate. Furthermore, upon removal of the shear stress, these compositions will rapidly recover to their initial viscosity. One method of applying a hair styling gel entails placing the hair gel in the hands, distributing the gel over the hands (applying shear) to form an even film, and then applying the film by passing the hands through the hair. This property allows such compositions to be easily transferred from fingers and palms during application to the hair. Consequently, hair fixative polymers suitable for all around use and ease of application, especially in gel formulations, may be limited primarily to neutral (i.e., uncharged, nonionic) polymers, such as PVP, and PVP/VA. However, these nonionic polymers are marginally effective in retaining a hair style or curl, impart a tacky, sticky feel to hair at conditions of relatively high humidity, and a raspy, harsh feel to dry hair. Additionally, the need for viscosity thickening or gellant additives increases the risk of leaving an unwanted residue or a dull film on the hair.
A prior art attempt to achieve a crosslinked acrylate polymer that is both a hair fixative and thickener is disclosed in U.S. Pat. No. 3,726,288 to Nowak, et al. However, the polymers disclosed are produced by an organic solvent based polymerization process using a toxic organic solvent (benzene) and, while thickening was achieved, hair fixative properties were weak (curl retention of less than 50% after 0.5 hours at 72° F. (about 22° C.) and 90% relative humidity).
Anionic polymers also have disadvantages, such as high water solubility, and therefore, low substantivity on hair fibers, resulting in low humidity resistance and generating a crust and flaking due to easy elimination from the hair by brushing and combing.
There is an ongoing need and desire, therefore, for a rheology modifying, hair setting polymer providing both thickening and effective hair fixative properties. In addition, there is a need for an anionic styling polymer that is compatible with anionic rheology modifiers or thickeners that also provides esthetically pleasing smooth gel appearance including clarity, hair fixative properties and good shear thinning rheology properties. Surprisingly, it has now been found that anionic acrylic copolymers polymerized in the presence of two different classes of crosslinking monomers and/or having a specific viscosity (ηsp) ranging from about 1 to 8 (measured in DMSO solvent) offer aesthetically pleasing smooth gel formulations with high clarity in addition to hair styling efficacy and stiffness. These crosslinked acrylic polymers overcome the disadvantages (unacceptable and unpleasant fixative, gel, and aesthetic properties) associated with the current commercially available hair styling polymers.